This invention relates generally to automotive safety devices and in particular to seatbelt safety devices for protecting vehicle occupants.
Seatbelt devices used to secure vehicular occupants in their seats typically comprise a single continuous length of webbed belt, one end of which is rigidly attached to the vehicle frame and the other end attached to an automatic retractor also mounted to the vehicle frame. The belt passes through a slot formed in a metal tongue that is plugged into a latch mounted to the floor of the vehicle on the side of the seat opposite the retractor and the rigid mount. The rigid mount, latch and retractor thus form a 3-point restraint.
It is generally preferable to mount the automatic retractor so that the seatbelt webbing is paid out over the shoulder of the occupant so that the occupant is freely able to lean forward and backward without the necessity of paying the seatbelt webbing in and out across the occupant's lap and through the slot in the latch tongue as would be necessary with a floor mounted retractor. Consequently, the most popular front seat passenger restraint systems comprise a rigid mount at the floor and a retractor mounted proximal to the floor in the area of the B-pillar of the vehicle. The retractor pays out and retracts the seatbelt webbing typically through a D-ring attached to the B-pillar above the area of the occupant's shoulder.
Conventional seatbelt webbing measures approximately 2 inches across its width. This two inch dimension is, however, a compromise between comfort and function. It has long been recognized that because of this limited width, the seatbelt webbing places enormous local loads on the passenger when restraining the passenger in a collision. Yet, ordinary webbing cannot be made substantially wider without rendering the seatbelt too cumbersome to use. In efforts to solve this problem, inflatable seatbelt apparatus have been proposed.
U.S. Pat. No. 3,841,654 to Lewis discloses a vehicle safety system in which a seatbelt has an inflatable section that is normally maintained in an uninflated state. The seat belt is positioned about a wearer when the wearer is seated in a seat within the vehicle. Inflating means are provided that are capable of inflating the inflatable section prior to any substantial forward motion of the seatbelt wearer relative to the seatbelt. By providing an inflatable belt, the load of the occupant against the seatbelt is distributed over a much wider area and, therefore, the occupant is much less likely to be injured by the seatbelt.
Because of the industry preference for seatbelt retractors that pay out and retract the seatbelt over the occupant's shoulder, the most practical location to mount the inflator for an inflatable seatbelt is near the fixed end of the belt which is attached directly to the vehicle frame near the floor. This substantially simplifies the design of any electrical interconnections or other connections between the inflator and the vehicle. Unfortunately, mounting of the inflator at the stationary end of the seatbelt webbing dictates that, during a collision, gas from the inflator must pass through the lap portion of the seatbelt and past the bend at the tongue in order to inflate the most critical part of the inflatable seatbelt, namely that portion of the seatbelt across the occupant's torso.
U.S. Pat. No. 5,383,713 to Kamiyama, et al. discloses an inflatable seatbelt apparatus comprising a floor mounted inflator coupled to a seatbelt airbag in which the eyelet in the tongue has a movable flap that opens to permit gas from the inflator to enter the torso portion of the seatbelt airbag. U.S. Pat. No. 5,474,326 to Cho, discloses a seatbelt airbag having a tongue eyelet equipped with a breakaway flap that opens during inflation to allow gas to pass from the lap portion of the belt into the torso portion of the belt. Although Kamiyama and Cho provide for a larger aperture through the eyelet in the seatbelt tongue, neither provide a substantial solution to the problem of the fabric pinching around the tongue, which will inherently impede gas flow. U.S. Pat. No. 6,340,173 to Specht, discloses a seatbelt airbag in which the lap portion of the belt includes a non-collapsing internal tube in the lap portion of the belt. The tube directs the output from the inflator into the torso portion of the belt. The rigid internal tube, however, renders the lap portion of the seatbelt bulky and awkward to wear.
Accordingly, what is needed is an inflatable seatbelt apparatus that reliably inflates the torso portion of the inflatable seatbelt, yet remains flat and comfortable to wear when uninflated.